docs: def startInstance(self, name=None,
              location=None,
              familyName=None,
              styleName=None,
              fileName=None,
              postScriptFontName=None,
              styleMapFamilyName=None,
              styleMapStyleName=None,
  
              ):
          """ Start a new instance.
              Instances can need a lot of configuration.
              So this method starts a new instance element. Use endInstance() to finish it.
  
              *   name: the name of this instance
              *   familyName: name for the font.info.familyName field. Required.
              *   styleName: name fot the font.info.styleName field. Required.
              *   fileName: filename for the instance UFO file. Required.
              *   postScriptFontName: name for the font.info.postScriptFontName field. Optional.
              *   styleMapFamilyName: name for the font.info.styleMapFamilyName field. Optional.
              *   styleMapStyleName: name for the font.info.styleMapStyleName field. Optional.
          """
          if self.currentInstance is not None:
              # We still have the previous one open
              self.endInstance()
          instanceElement = ET.Element('instance')
          if name is not None:
              instanceElement.attrib['name'] = name
          if location is not None:
              locationElement = self._makeLocationElement(location)
              instanceElement.append(locationElement)
          if familyName is not None:
              instanceElement.attrib['familyname'] = familyName
          if styleName is not None:
              instanceElement.attrib['stylename'] = styleName
          if fileName is not None:
              instanceElement.attrib['filename'] = self._posixPathRelativeToDocument(fileName)
          if postScriptFontName is not None:
              instanceElement.attrib['postscriptfontname'] = postScriptFontName
          if styleMapFamilyName is not None:
              instanceElement.attrib['stylemapfamilyname'] = styleMapFamilyName
          if styleMapStyleName is not None:
              instanceElement.attrib['stylemapstylename'] = styleMapStyleName
  
          self.currentInstance = instanceElement